Data storage and retrieval systems are used to store information provided by one or more host computer systems. Such data storage and retrieval systems receive requests to write information to one or more data storage devices, and requests to retrieve information from those one or more data storage devices. Upon receipt of a write request, the system stores information received from a host computer in a data cache. In certain implementations, a copy of that information is also stored in a nonvolatile storage device. Upon receipt of a read request, the system recalls information from the one or more data storage devices and moves that information to the data cache. Thus, the system is continuously moving information to and from a plurality of data storage devices, and to and from the data cache.
Certain standards applicable to the interconnection of the plurality of data storage devices to the data storage and retrieval system require that two LEDs be interconnected with each data storage device, where one LED visually indicates whether the interconnected data storage device is operable, and another LED visually indicates whether the interconnected data storage device is in use. Thus, a data storage and retrieval system comprising (X) data storage devices, and compliant with the Standard comprises (2X) LEDs. The failure of any one of those (2X) LEDs, however, may require that, in order to remain compliant with the standard, one or more data storage devices be taken out of service to repair or replace that failed LED.
What is needed is an apparatus that complies with the interconnection standard, but that does not require that one or more data storage devices be taken out of service in the event a single LED fails.